There is substantial interest in the petroleum industry for converting heavy hydrocarbonaceous feedstocks to lower boiling liquids. One type of process suitable for hydroconversion of heavy feedstocks in a slurry process using a catalyst prepared in a hydrocarbon oil from a thermally decomposable metal compound catalyst precursor. The catalyst is formed in situ in the hydroconversion zone. See for example, U.S. Pat. Nos. 4,226,742 and 4,244,839.
It is also known to use such catalysts in hydroconversion processes (i.e., coal liquefaction) in which coal particles are slurried in a hydrocarbonaceous material. See, for example, U.S. Pat. Nos. 4,077,867 and 4,111,787.
Further, U.S. Pat. Nos. 4,740,295 and 4,740,489, both of which are incorporated herein by reference, teach a method wherein the catalyst is prepared from a phosphomolybdic acid precursor concentrate. The precursor concentrate is sulfided prior to the final catalyst formation. This presulfiding step is taught to produce a catalyst having greater control over coke formation. The sulfiding agent in these two patents requires a hydrogen-sulfide containing gas or a hydrogen-sulfide precursor and the resulting catalyst concentrate is used for hydroconversion of heavy hydrocarbonaceous materials to lower boiling products.
The term "hydroconversion" with reference to a hydrocarbonaceous oil, is used herein to designate a catalytic process conducted in the presence of hydrogen in which at least a portion of the heavy constituents of the oil is converted to lower boiling products. The simultaneous reduction of the concentration of nitrogenous compounds, sulfur compounds and metallic constituents of the oil may also result.
The term "hydroconversion" with reference to coal is used herein to designate a catalytic conversion of coal to normally liquid products in the presence of hydrogen.
All boiling points referred to herein are atmospheric pressure equivalent boiling points unless otherwise specified.
It has been found that introducing a catalyst precursor as a concentrate in a hydrocarbonaceous oil into a hydroconversion zone containing a heavy hydrocarbonaceous chargestock has certain advantages when compared with a process wherein the catalyst precursor is introduced into the hydroconversion zone without first forming a concentrate; that is, by introducing the catalyst precursor directly into the feed in the reactor. The advantages include: (i) ease of mixing the precursor with a small stream instead of the whole feed; (ii) the ability to store the precursor concentrate for future use and/or activity certification; and (iii) the ability to use a hydrocarbonaceous oil, other than the feedstock, as dispersing medium for the catalyst precursor, which hydrocarbonaceous oil other than the feedstock can be more optimum for developing catalyst activity.
Further, it has also been found that converting a catalyst precursor concentrate to a catalyst concentrate comprised of solid catalyst particles dispersed in a hydrocarbonaceous oil and subsequently introducing a portion of this catalyst concentrate into the hydrocarbonaceous chargestock to be hydroconverted, with or without coal, will provide certain additional advantages, such as greater flexibility of conditions. Such advantages include: (i) use of higher concentrations of sulfiding agent than those concentrations that could practically be used to treat the total chargestock; (ii) flexibility of heat balance; and (iii) economy of energy. Treatment of only the catalyst precursor concentrate to produce the catalyst instead of treating the entire feedstock containing the catalyst precursor, permits reduction of equipment size. Furthermore, preparing a catalyst concentrate permits storage of the catalyst concentrate for use as needed on-site or to send to another site.
It has also been found by the inventors hereof that when elemental sulfur is used as the sulfiding agent in the preparation of the catalyst concentrate of this invention, a critical range of atomic ratio of sulfur to metal of the metal compound used herein exits in which hydroconversion is enhanced. This critical range is from about 1/1 to 8/1 sulfur to metal. Use of elemental sulfur has the advantages of ease and simplicity of catalyst preparation. It also has the advantage of being less hazardous because there is no need to handle hydrogen sulfide under elevated pressures, as is required by prior art processes.